Counting yeast cells and stepping up the starter

[emengee]

Beersmith says I need 639.1 Billion yeast cells of Wyeast London ESB 1068 for my 75 litre batch. 45 packets of yeast when using a starter. The last couple of batches, I have used 2 pakets and made a 2 litre starter the way it is described. It worked out ok, but as I now only have one more pack left, and none more readily available, will I get the same result by using the one packet and stepping it up four times, reducing the wort back each time so I end up with a 2 litre starter.
I will be harvesting the yeast for future from the brew currently in the fermentor, but I have to get this last batch done for a promise, and to a deadline, so I can not wait to mail order more yeast in.
How does one count the yeast cells?
Has anyone come accross or can point me to a good source of info on this subject.

 

[micblair]

45 packets! I've brewed 600 L batches at Federation uni with 2 smack packs of ESB into a 25 L plastic fermenter as our starter with around 15 L of wort, and fermentation was seen by the following day.

If you really want to get into yeast counting, you will need a microscope with at least a 400x objective, methylene blue for viability staining, haemocytometer, volumetric pipettes for serial dilution, EDTA or H2SO4 for deflocculating yeast samples and a some form of counting system. You could spend up to a $1000 on just this stuff alone.

I would invest in a pH probe and be looking at your pH drop in the first 12-24 hours as a measure of yeast vitality etc.